CAST IRON 150

[Larry Perkins]

Were the 150 bikes a whole different cylinder or was it possible to punch the 125 out that far?  Also what head was used?  Thanks!

Larry P

[Kip Kern]

Larry,
A bored out cast 125 cylinder with slightly re machined 125 head. Seen variations of pistons used including Yamaha.

[Larry Perkins]

Thank you Kip!

Larry P

[Paul Danik]

Hi Larry,

   You didn't ask so maybe you are already up to speed on the piston choice for the 152cc conversion, but just in case here is my 2 cents... I am sure you are aware of much of this.....but just want to be as correct as possible. I encourage others to correct anything that I am mistaken about.

   Originally Penton used a Yamaha piston to create the 152cc topend. The Yamaha piston had a larger wrist pin than the Sachs piston so an early crank with a top end bushing was needed as the bushing was reamed out to fit the Yamaha pin. The Sachs cranks with the aluminum rod were the ones with a top end bushing. I am thinking that with the Yamaha piston you may need to move the piston ring locating pin or pins as well, but I don't know that for sure, just a MAYBE !

  The other issue with the wrist pin on the Yamaha piston is its location in the piston, the base of the cylinder needed to be machined to obtain the correct deck height.

   Enter the Wiseco piston, the Wiseco piston for this application had the same size wrist pin as the Sachs piston and the pin was located so as to require NO cylinder base machining. Obviously a much easier conversion.

   Most of the original 152cc engines that were done by Penton that I have seen have a Sachs high compression head on them. Some of the very early ones had a Puch head on them that must have boosted the compression as well. I think maybe Sachs created their high compression head when they saw the need for it, but that is just my opinion. I am not sure about what head modification was needed with the Sachs high compression head for this application, or if one was indeed needed. Hopefully an expert will chime in with some specifics.

  I have also seen a few 152cc topends that were created using the later alloy cylinder, but they are apparently quite rare.

   As a side note, I was once told that George Singler, who apparently was very well versed with the Yamahas of that era, had some input into the creation of the 152cc Sachs engines by Penton Imports. The gent who told me that piece of information is quite credible, just wanted to make mention of it.

  Side note #2, I was also told that the reason there were so many Steel Tank Berkshire gas tanks floating around, such as the ones that Al Buehner had for a number of years, is that Penton used the unsold Berkshires as the donor machines to create the early 152cc Penton Jackpiners. As I am sure you know, there was only a small price difference between the 100cc and 125cc machines and in reality they would have cost the same to build at KTM. I don't think I have any of the original 152cc machines that Penton Imports built, but if I do I will want to see what the side cover plate indicates, 97 cc???  Possibly some of you with such engines can chime in, I don't think they would have created a new plate just for those engines, but one should never underestimate what Ted Penton and crew might do....

Paul

[Carl Hill]

I have a couple of those Wiseco pistons if anybody is interested.

[t20sl]

Paul:
Yes for sure you have to relocate the pins that locate the rings.  I remember doing that and it was a chore to get the old pins out of the Yamaha 305 Big Bear pistons.